Method and apparatus for refractory metal deposition

ABSTRACT

A laser induced direct writing pyrolysis of a refractory metal or metal silicide on substrates is described. Typical reactants comprise flowing WF 6 , MoF 6  or TiCl 4  with SiH 4  and an inert gas, such as Argon. A preferable substrate surface is a polyimide film. The refractory metal film may comprise low resistivity W, M, or Ti, or silicides thereof, having a predetermined resistance depending on the relative ratio of reactants. The invention is useful, inter alia, for repair of defective circuit interconnects, and formation of interconnects or resistors on substrates.

The Government has rights in this invention pursuant to Contract NumberF19628-85-C-0002 awarded by the Department of the Air Force.

BACKGROUND ART

In the manufacture of semiconductor integrated circuits, low resistanceinterconnection between circuit elements formed on or in the layers ofthe semiconductor material is essential. Generally, suchinterconnections are made as a step in the process of microcircuitfabrication utilizing well-known photolithographic masking, etching, andmetal deposition techniques. In the past several years, direct writingof interconnects by local energy stimulus of a laser beam has been anactive area of research. Such a technique is extremely useful forrepairing defects or modifying existing integrated circuits to avoid thenecessity for, and complexity involved in, conventionalphotolithography.

The most widely applied direct writing process has been the pyrolyticdeposition of polysilicon from silane. When the silane gas is heavilydoped with a material such as diborane, moderately conductiveinterconnects (500 microohm-cm at best) are deposited. This system hasbeen applied to repair or modification of CMOS gate array circuits(Ehrlich et al. (1982).sup.(1) and other electronic devices.

Many experimental approaches for directly depositing metals have beenattempted in this time period. Most such approaches have been very slowdue to chemical or optical limitations, or require use of exotic orhighly toxic materials. In virtually every case the writing speed and/orthe total thickness of the interconnect material is well belowtechnologically useful values. In the case of polysilicon interconnects,the speed and thickness are adequate, but the conductivity is 2 decadesbelow that of metals.

Tungsten and tungsten silicide have received increasing attention asVery Large Scale Integrated (VLSI) interconnection materials, owing totheir low contact resistance to silicon, low susceptibility toelectromigration, and high conductivity (6 and 70 microohms cm,respectively)..sup.(2)

There have been chemical vapor deposition processes (CVD) for creatinglayers of tungsten and its silicides for several years, for broad areacoatings [for example, see Shaw and Amick (1970)].sup.(4) The growthrates are usually in the range of 100 nm/min (or roughly 6micrometers/hr). Various attempts to bring these materials into thediscretionary direct writing domain have been published. Berg & Mattox(1973).sup.(5) deposited tungsten using an infrared laser and a WF₆ /H₂gas mix. In this case, the thicknesses were limited to 100 nm, and thelaser power and resultant local heating were extremely high. Inaddition, good metallic conductivity was not obtained consistentlyunless high temperature furnace annealing followed laser-induceddeposition. Deutsch & Rathman (1984).sup.(5) performed a comparison ofconventional CVD tungsten and an ultraviolet-laser enhanced depositionof this material. In their case, the laser was used in a broadfixed-spot mode, and again high temperatures were required to obtain lowresistivity material. The growth rates/thicknesses were very similar tothose stated above.

More recently, there has been activity in applying an interestingreaction wherein WF₆ reduces solid silicon.sup.(6-8), leaving a tungstencladding over exposed silicon, but has no effect on backgroundmaterials, such as SiO₂. This is a selective deposition reaction whichforms tungsten on silicon by the silicon reduction of WF₆ :

    3Si+2WF.sub.6 →3SiF.sub.4 ↑+2W

This process has been extensively investigated [Tsao & Busta(1984).sup.(6) ], and many others, for use in improving the conductivityof polysilicon interconnects, which are frequently used in silicondevices. Herman et al. (1984).sup.(3b), and Liu et al. (1985).sup.(3a)have used the reaction to directly write tungsten coatings on bulksilicon, but the thickness is limited to 100 nm, and in most circuitapplications, one requires electrical isolation between the siliconsubstrate and the interconnection metal to prevent shorting of circuitdevices.

Therefore, despite the above intensive investigatory efforts, a suitableprocess for deposition of a low resistivity refractory metal patternwith good adherence on a substrate at high linear writing rates and atsufficiently low temperature to avoid damaging the substrate, has notbeen reported.

DISCLOSURE OF THE INVENTION

This invention relates, in general, to a catalyzed refractory metalprocess for depositing a low resistance refractory metal or a refractorymetal silicide of predetermined resistance on a substrate in a reactionchamber. The refractory metal may be tungsten (W), molybdenum (Mo), ortitanium (Ti). A flowing gaseous fluoride or chloride compound of therefractory metal and a silicon containing gas, such as silane (SiH₄),disilane (Si₂ H₆) or dichlorosilane (SiCl₂ H₂) are introduced into areaction chamber. Photon energy from a laser beam is scanned across thesubstrate along the path in which the desired metal pattern is to bewritten. The energy from the laser beam is sufficient to initiate areaction between the two reactant gases and localizes and guides thereaction, while the Si compound provides a catalyst to sustain thereaction resulting in deposition of the refractory metal along the pathof the laser beam.

For deposits of greater than 200 nm thickness, we have found that it isessential that a proper substrate surface of an inert stress-relievingmaterial, preferably a polyimide, be provided on the substrate to assuregood adhesion of the refractory metal.

Suitable ratios of reactants, volumes of gases and ranges of laserscanning speed to provide optimum performance will now be explained indetail in connection with the drawings. In this explanation, thepreferred Refractory Metal Gaseous (RMG) compound is WF₆ and the Sicompound is silane, since most of our experiments were carried out withthese materials. The process extends, however, to chemical analogues,such as silane/molybdenum hexafluoride or silane/titanium tetrachloridemixtures. Experimental results on the former yielded direct depositionby laser pyrolysis at rapid rates characteristic of the silane-activatedbinary reaction of the present invention. Other analogies contemplatedinclude use of Ge-containing gaseous compounds, such as GeH₄ or GeCl₂H₂, in place of the Si-containing reactant gas.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1(A-D) are cross-sectional views of semiconductor circuits showinghow the process of the invention can be employed to write metal patterns(1A) or repair existing patterns (1B-C).

FIG. 2 is a plot of resistivity of the deposited pattern versus ratio ofreactants (WF₆ /SiH₄) at three different scanning speeds.

FIG. 3 is a plot of the cross-sectional area of the deposited patternversus ratio of reactants (WF₆ /SiH₄) at three different scanningspeeds.

FIG. 4 is a plot of the cross-sectional area of the deposited patternversus laser power for a fixed ratio (3:1) of reactants.

FIG. 5 is a plot of resistivity versus reactant ratio for three dilutionvalues with a fixed gas flow rate.

BEST MODE FOR CARRYING OUT THE INVENTION

The apparatus for performing the laser induced CVD pyrolysis of thereactants employed in the present invention is similar to that describedin previous direct-write laser applications (See D. J. Ehrlich et al.,"Laser Microphoto Chemistry For Use In Solid-State Electronics", IEEE J.Quantum Electronic QE-16 p. 1233, 1980). A 488-nanometer Argon-ion laserwas used in the experiments in which rapidly flowing SiH₄ /WF₆ mixture,with inert gas (Argon) buffering is coupled into a reaction chamber,such as a deposition cell, in which a substrate is provided. Thesubstrate deposition surface is disposed perpendicular to the focusedArgon-ion laser beam which enters the reaction chamber through a lighttransparent window. The reactant gases flow past the focused beam. Thelaser beam is fixed in space and the substrate and chamber are preciselymoved in relation to the beam in the path of the desired depositionpattern. The gas flow is electronically controlled and ample exhaustdilution and continuous vacuum oil filtering are employed to eliminateexplosive reactions. Typically, the pressure was maintained in the orderof 380 torr, and gas flows in the order of 0.4 sccm SiH₄, 1 sccm WF₆ and10 sccm Argon.

In our early experiments using SiH₄ and a flowing WF₆ inert gas mixture,under certain conditions, the deposits, or at least their margins, weremetallic in appearance. These shiny films were very thin, similar tothat seen in older laser-CVD works, as opposed to the main deposit,which was deposited at very rapid rates (1 micrometer in 20milliseconds). It was also noted that the laser power required toinitiate this process was a decade below that needed for polysilicondeposition on similar substrates. The major flaw in the experimentalmaterial was its adhesion to the substrate. The fluorine, or fluorideswhich result from the pyrolysis attack silicon oxide and silicon nitridesubstrates. These materials also have little elasticity at the reducedsurface temperatures (about 175° C.) encountered at the low laser powersutilized in the process, i.e., about 40 mW.

We therefore searched for a material which would have the requisitestress relieving properties at this relatively low temperature and stillbe sufficiently inert to resist degradation by attack from the volatilefluorines or fluorides produced in the reaction. In a series ofexperiments, we explored the use of SiO₂, Si₃ N₄, and various organicpolymer films for these purposes. Although polymer films were known tohave potentially advantageous properties for stress relief andinertness, it was found that when these films were laser irradiated inair or in a vacuum, they were degraded beyond use at laser power levelswell below those required to initiate deposition. Nonetheless, we havefound that when irradiated in a WF₆ /SiH₄ ambient, one class of thesematerials, namely polyimide films, have excellent utility asintermediate dielectric layers for stress relief and protection ofsubstrates from chemical attack. Apparently, the tungsten depositionreaction itself, or a coincident side reaction, prevents the degradationof these polyimide films at laser powers sufficiently high to permitthis use.

This polyimide material may be spun-on and baked, similar to thetechnique for applying photoresist to substrates. It has gainedincreasing use in silicon and GaAs device processing due to its ease ofuse and chemical durability. The laser-direct-writing of tungsten onthis material works extremely well, and has been repeatedly accomplishedin our laboratory for several months with totally reproducible results.The polyimide's resilience compensates for the inherent stress betweenthe tungsten and the underlying substrate, and protects the substratefrom fluoride attack. The low laser power required for deposition (20 mWto 500 mW) leaves the polyimide undamaged. We have determined bytemperature bias experiments that the initiation temperature for thereaction is in the range of 175°-225° C., and polyimide beginsdecomposing at 475° C. Substrates varying from silicon, to GaAs, glass,and even cast epoxy, have been successfully metallized using the newprocess. The use of polyimide also allows for multi-levelinterconnection.

As shown in FIG. 1A, a device 30 may be fabricated from a substrate 12upon which a polyimide layer 14 is formed. The substrate may compriseany of the well-known integrated circuit materials requiringinterconnections, such as GaAs, Si, and may even comprise glass orepoxy. A via hole 24 is formed through the polyimide 14 to provideconnection to metal contact region 28 in substrate 12. A first tungstenlayer pattern 16 is directly written on the polyimide, in accordancewith the above-described process; and the via hole 24 is filled withtungsten connection zone 28 to pattern 16. Next, pattern 16 isovercoated with a second polyimide layer 18 and a second metal layerpattern 20 is laser-written, in accordance with the invention. Layer 20either crosses the first metal without electrical contact, or connectswith the first metal thorugh a laser-ablated via hole 22. Such two levelinterconnections are essential in integrated circuits of all but themost trivial complexity, unless unusual provisions are made in designsto allow use of only one metal layer.

As shown in FIGS. 1(B-D), defective devices 30 fabricated in accordancewith well-known prior art techniques, may be repaired in accordance withthe process of the invention. Device 30 may, for example, comprise anintegrated circuit in which p/n diodes 33 are formed in a well-knownmanner on a substrate 26, such as by diffusion of p and n doped siliconregions utilizing photolithography to define the diodes. Metal contacts35 a,b are provided on the p and n diode elements, respectively; and aprotective layer 38 of SiO₂ or Si₃ N₄ is formed in a conventional mannerover the interconnecting metal pattern 36.

Suppose, however, that one of the interconnecting patterns is defectiveor missing. This defect can be corrected by forming a polyimide film 40over the SiO₂ layer 38 (FIG. 1C) and then opening via holes 42 to theportions of the circuit to be connected; for example, the n-contact ofone diode 33a and the p-contact of another diode 33b. Next, FIG. 1D, thedesired metal tungsten pattern 50 is written in accordance with theprocess, to fill in the via holes 42 and interconnect the two contacts.As optional encapsulating coating 52 may then be applied over thepattern 50. Alternatively, as will be described below, the pattern 50may be made resistive by varying the ratio of WF₆ to SiH₄, thusproducing precision resistors between elements.

To determine optimum process parameters for the direct laser inducedwriting process, certain parameters were varied in a controlled manner.

The parameter of greatest importance is the WF₆ /SiH₄ ratio. FIG. 2shows the bulk resistivity (in microohm-cm) plotted versus the W/Siratio. As an additional parameter, the writing speed is varied from 25μm/sec (curve "O") to 50 μm/sec (curve "+") to 100 μm (curve Δ). Thelaser power in these experiments is also increased roughlyproportionally to the speed increase to keep the deposition consistentbetween runs. Notable on this curve is the parabolic inverserelationship between the resistivity and the W/Si ratio. Also observedis the marked improvement in bulk conductivity with process speed. Athigher speeds, the samples appear as specular metals, whereas at lowerspeeds, they appear dark, with a slightly rough surface.

To ascertain the role of speed/composition in determining the amount ofmaterial deposited, the data in FIG. 2 is re-plotted in FIG. 3. FromFIG. 3 it can be seen that the cross-sectional area of the depositedlines is essentially invariant with scan speed for a given W/Si ratio,so that it may be concluded that the intrinsic properties of thematerial are not immediately related to the size of the deposit.

FIG. 4 is a plot at a fixed W/Si ratio (approximately 5:1) and a fixedlaser scanning speed (50 micrometers/s). The resultant cross-sectionalarea of the deposits is shown to be linearly related to the laser power.Note that the optical efficiency of the experimental system isapproximately 25 percent, so that maximum power on this line isapproximately 300 milliwatts. In virtually every case, the processlatitude is remarkably wide; speed or power variations of 20 percentgenerally represent no difficulty, and ultra-precise speed regulation inthe sample or beam scanning is not required. This is a result of theself-driven nature of the deposition reaction.

The total "richness" of the gas mix appears not to be a criticalparameter. FIG. 5 shows the resistivity versus W/Si ratio as before, thelines range over a factor of 3 in active/buffer gas concentrations. Nosignificant effect is observed in this range. At extremely high buffergas levels, the reaction is suppressed, and at very low levels, the riskof spontaneous reaction (explosion) is high. We have found that anominal 10:1 buffer/active gas ratio is optimal.

By manipulating process conditions, we have obtained tungsten depositswith bulk resistivity down to 25 microohm-cm, which is about twice theusual value of thin film tungsten. We have also adjusted conditions byincreasing the amount of Si (i.e., lower ratio of WF₆ to SiH₄) to obtainresistivities well above 100 microohm-cm, allowing direct deposition ofresistors on polyimide. It should be noted that all of our results areobtained in the absence of any further annealing.

In a manner similar to the tungsten hexafluoride/silane laser-inducedreaction described earlier, we have performed experiments to depositmolybdenum and titanium by employing a mixture of silane and theappropriate metal halide.

Using a flowing gas mixture at 380 torr absolute pressure, composed of 1sccm (standard cubic centimeter/minute) MoF₆, 0.4 sccm SiH₄, and 10 sccmAr, an opaque deposit was formed on a polyimide-coated silicon sample.

Similarly, an experiment using TiCl₄ and SiH₄ was undertaken. At 375torr total pressure, 5 sccm of Ar was passed through a bubbler vialfilled with TiCl₄, in order to carry its vapor to the reaction cell. 5sccm Ar and 0.5 sccm SiH₄ were additionally mixed in. Under 488-nm laserirradiation on the substrate, an opaque deposit was formed.

Additionally, excimer laser radiation (ArF, wavelength=193 nm) wasemployed in the WF₆ /SiH₄ deposition ambients, as well as the analogousTi and Mo experiments. At a pulse repetition rate of 50 Hertz, theaverage power was adjusted to be in the range comparable to that used inthe visible (Argon) laser cases described above. With a microscopesystem fitted with all-reflective optics, a focused spot was scanned asabove. The deposition reaction took place in much the same manner asdescribed above, with identical pressures and flows of the constituentgases.

Hybrid circuits were fabricated for direct-written tungsteninterconnections. Indivudal components were mounted in a suitablecarrier, such that the active surfaces were all coplanar (flush) withthe carrier's top surface. The carrier may be a silicon wafer withphotolithographically defined etched holes into which the components areplaced, and then coated with polyimide, both for affixing thecomponents, as well as providing the protective coating for the tungstendeposition process. Alternatively, we employed the technique of castingthe components monolithically in a slab of epoxy, or alumina-filledepoxy, followed by the usual overcoat. The desired contact areas, orbonding pads, are cleared of polyimide, either photolithographically, orby using excimer laser radiation, to directly ablate the polyimide abovethe contact regions. The interconnection then proceeds as describedabove.

EQUIVALENTS

This completes the description of the preferred embodiments of theinvention. Those skilled in the art will be able to devise modificationsthereof without departing from the spirit and scope of the invention.For example, some integrated circuits presently employ a polyimidelayer, therefore, the process of the invention will find directapplicability to the repair of defects on such circuits without thenecessity of special substrate preparation. The substrate may be formedof many hybrid circuits or chips, separately fabricated and adhered to acarrier made of glass, semiconductor, ceramic, epoxy, or other suitableelectrically insulating material.

Accordingly, the invention is not intended to be limited except asprovided in the claims hereto.

.sup.(1) D. J. Ehrlich, J. Y. Tsao, D. J. Silversmith, J. H. C.Sedlacek, R. W. Mountain and W. S. Graber, "Direct-Write Metallizationof Silicon MOSFETs Using Laser Photodeposition", IEEE Electron DeviceLett., Vol. EDL-5, pg. 32,1984.

.sup.(2) S. Sachdev and R. Castellano, "CVD Tungsten and TungstenSilicide for VLSI Applications", Semiconductor International, Vol. 8,pg. 306, 1985.

.sup.(3) (a) Y. S. Liu, C. P. Yakymyshyn, H. R. Phillipp, H. S. Cole,and L. M. Levinson, "Laser-Induced Selective Deposition of Tungsten onSilicon", J. Vac. Sci. Technol., Vol. B3, pg. 1441, 1985. (b) I. P.Herman, B. M. McWilliams, F. Militsky, H. W. Chin, R. A. Hyde and L. L.Wood, "Wafer-Scale Laser Pantography: Physics of Direct Laser-WritingMicron-Dimension Transistors" in Laser-Controlled Chemical Processing ofSurfaces, A. W. Johnson, D. J. Ehrlich, and H. R. Schlossbert, eds. NewYork: North-Holland, 1984.

.sup.(4) J. M. Shaw and J. A. Amick, "Vapor Deposited Tungsten as aMetallization and Interconnection Material for Silicon Devices", RCAReview, Vol. 31, pg. 306, 1970.

.sup.(5) R. S. Berg and D. M. Mattox, "Deposition of Metal Films byLaser-Controlled CVD", 4th Int. Conf. Chem. Vapor Dep. pg 196 (1973), G.F. Wakefield and J. M. Blocker, eds.

.sup.(6) K. Y. Tsao and H. H. Busta, "Lower Pressure Chemical VaporDeposition of Tungsten on Polycrystalline and Single Crystal Silicon viathe Silicon Reduction", J. Electrochem, Soc. Vol. 141, pg. 2702, 1984.

.sup.(7) W. T. Stacy, E. K. Broadbent, and M. H. Norcott, "InterfacialStructure of Tungsten Layers Formed by Selective Low Pressure ChemicalVapor Deposition", J. Electrochem. Soc., Vol. 132, pg. 444, 1985.

.sup.(8) M. L. Green and R. A. Levy, "Structure of Selective LowPressure Chemical Vapor-Deposited Films of Tungsten", J. Electrochem.Soc., VOl. 132, pg. 1243, 1985.

.sup.(9) T. F. Duetsch and D. D. Rathman, "Comparison of Laser-Initiatedand Thermal Chemical Vapor Deposition of Tungsten Films", Appl. Phys.Lett., Vol. 45, pg. 623,1984.

We claim:
 1. The method of forming a refractory metal pattern on asemiconductor substrate located within a reaction chamber comprising thesteps of:(a) introducing a flowing gas mixture of two reactants and aninert gas into said chamber wherein the reactants comprise:(i) arefractory metal gaseous (RMG) compound, and a (ii) silicon (Si) orgermanium (Ge) atom containing gaseous compound, and (iii) wherein themetal for the RMG compound is taken from the class comprising: W, Mo,Ti; (iv) the ratio by volume of RMG compound to Si or Ge containinggaseous compound is between about 1:1 and 20:1; and (b) subjecting saidmixture to laser irradiation using a level of laser irradiation powerdirected toward said substrate and sufficient to initiate a localizedreaction between the two reactants; with the Si or Ge compound providinga catalyst to sustain the reaction, resulting in the desired patternbeing formed on said substrate by deposit of said refractory metal andwherein the temperature at which the reaction occurs and the refractorymetal pattern is formed is below about 475° C.
 2. The process of claim 1wherein the substrate has an exposed polyimide surface upon which thepattern is formed.
 3. The process of repairing interconnection defectsin a substrate comprising the steps of:(a) forming a stress relievingprotective layer on said substrate; (b) forming openings in theprotective layer to points on the substrate which should beinterconnected to repair the defect; (c) depositing a refractory metalin said openings and on said protective layer by low temperaturepyrolysis at a temperature below 500° C. of a mixture of a flowing inertgas and a refractory metal gaseous compound and a silicon or germaniumcontaining gaseous compound in a ratio by volume by greater than 1:1refractory metal gaseous compound to silicon or germanium gaseouscompound using a low power laser beam directed at the substrate toinitiate and direct a localized reaction of said mixture to produce arefractory metal interconnection pattern.
 4. The process of claim 3wherein the substrate is a multi-chip or hybrid carrier comprised ofglass, semiconductor, ceramic or epoxy material.
 5. The method offorming a pattern of tungsten on a substrate located within a reactionchamber comprising the steps of:(a) introducing a flowing gas mixture ofWF₆ and SiH₄ and an inert gas; and (b) subjecting said mixture to laserirradiation using a level of laser irradiation power sufficient toinitiate a localized reaction between the WF₆ and SiH₄ with the SiH₄providing a catalyst to sustain the localized reaction, resulting in thedesired pattern of low resistivity metal tungsten being formed on saidsubstrate and wherein the ratio of WF₆ to SiH₄ is at least 1:1 or higherby volume and the reaction occurs at temperatures below 500° C.
 6. Theprocess of claim 3 wherein the protective layer comprises a polyimide.7. The method of claim 5 wherein the ratio by volume of WF₆ to SiH₄ isbetween about 1:1 and 20:1.
 8. The process of providing interconnectionsfor regions formed in a substrate comprising the steps of:(a) forming apolyimide layer on said substrate; (b) forming openings to regions ofthe substrate to be interconnected; (c) depositing a refractory metal insaid openings and on said polyimide layer by low temperature pyrolysisat a temperature below 500° C. of a mixture of an inert gas and WF₆,MoF₆ or TiCl₄ and an Si containing gaseous compound using a low powerlaser beam directed at the substrate to initiate and direct a localizedreaction of said mixture to produce a non-silicide, refractory metalinterconnection pattern.
 9. The method of forming a refractory metalpattern on a semiconductor substrate located within a reaction chambercomprising the steps of:(a) introducing a flowing gas mixture of tworeactants and an inert gas wherein the reactants comprise:(i) arefractory metal gaseous compound, and a (ii) a silicon or germaniumatom containing gaseous compound, and (iii) wherein the refractory metalgaseous compound is taken from the class comprising: W, Mo, Ti fluoridesor chlorides; and (iv) the ratio by volume of the silicon or germaniumcompound compared to the refractory metal compound is 1:1 or less; and(b) imparting sufficient light energy to the reactants from a beam oflight directed at the substrate surface upon which the metal pattern isto be formed to initiate a localized reaction between the two reactants;with the Si or Ge atom containing gaseous compound providing a catalystto sustain the reaction, resulting in the desired pattern being formedon said substrate by deposit of a refractory metal pattern at atemperature below 500° C.
 10. The process of claim 9 wherein thesubstrate has an exposed polyimide surface upon which the pattern isformed.
 11. The process of claim 9 wherein the energy is imparted by alaser and the refractory metal gaseous compound is a metal fluoride orchloride compound containing a metal from the class of W, Mo or Ti andthe pressure in the chamber during the reaction is in excess of 100Torr.
 12. The process of repairing interconnection defects by forming aninterconnection metal pattern on a substrate comprising the steps of:(a)forming a stress relieving protective layer on said substrate; (b)forming openings in the protective layer to regions on a substrate whichshould be interconnected to repair the defect; (c) depositing a lowresistivity refractory metal in said openings and on said protectivelayer by localized low temperature pyrolysis at a temperature below 500°C. of a mixture of a flowing inert gas and a refractory metal gaseouscompound and a semiconductor containing gaseous compound using low powerlaser energy directed at the substrate surface upon which the pattern isto be formed to initiate and direct the interconnection pattern.
 13. Theprocess of claim 12 wherein the sbustrate is a multi-chip or hybridcarrier comprised of glass, semiconductor, ceramic or epoxy material.14. The process of claim 12 wherein the protective layer is comprised ofa polyimide.
 15. The method of forming a pattern of tungsten on asubstrate located within a reaction chamber comprising the steps of:(a)introducing a flowing gas mixture of WF₆ and SiH₄ having a ratio byvolume of WF₆ to SiH₄ which is equal to or greater than about 1:1 and aninert gas; and (b) subjecting said mixture to sufficient power from alaser beam directed at the substrate to initiate a localized reaction ata temperature below 500° C. between the WF₆ and SiH₄, with the SiH₄providing a catalyst to sustain the reaction, resulting in the desiredmetal pattern of tungsten being formed on said substrate.
 16. The methodof claim 15 wherein the resistivity of the metallic pattern of W isabout 150 micro-ohm-cm or less.
 17. The process of providinginterconnections for regions formed in a substrate comprising the stepsof:(a) forming a polyimide layer on said substrate; (b) forming openingsto the substrate to regions to be interconnected; (c) depositing arefractory metal in said openings and on said polyimide by localized lowtemperature pyrolysis at a temperature below 500° C. of a mixture of aninert gas and WF₆, MoF₆ or TiCl₄ and an Si containing gaseous compoundusing a low energy laser pulse directed at the interconnections.